1. Field of the Invention
The present invention relates to a method and a system for machining (e.g., cutting or grinding) a workpiece with a machining device, and particularly to a method and a system suitable for machining a plurality of workpieces in an unmanned manner, i.e., without needing any human operators.
2. Discussion of Related Art
There is known a method and a system for machining, with a machining device, a number of workpieces in an unmanned manner. In one known example, a plurality of machining centers are arranged to provide a machining line, a plurality of workpieces are attached, in advance, to a plurality of blocks, respectively, and each block with one workpiece is carried in to, attached to, detached from, and carried out from, each of the machining centers, all by a robot. Though the robot may be adapted to additionally attach and detach a workpiece to and from each block, it is a general practice that a human operator attaches, in advance, a workpiece to each block and, after the workpiece attached to the each block is machined in an unmanned manner, the operator detaches the workpiece from the each block. In this machining method, the operator may attach and detach a number of workpieces to and from a number of blocks, respectively, in the daytime, and the workpieces attached to the blocks may be machined in an unmanned manner in the nighttime. In addition, it has been practiced to combine a conveying device and a robot, or employ a movable robot, to carry in, attach, detach, and carry out each workpiece to and from each of the machining centers.
However, the above-indicated machining method in which workpieces are attached in advance to blocks, respectively, suffers from a problem that each of the blocks needs to have a complicated structure. In addition, large-size equipments are needed to carry in, attach, detach, and carry out large-size blocks, which leads to increasing the cost of the equipments. Moreover, it is not always possible for a robot to carry in, attach, detach, and carry out each workpiece. Even in the case where a robot can do all of them, the robot may not stably hold a workpiece having a complicated structure, and an accident such as falling of the workpiece from the robot may occur during conveying of the workpiece. These problems most likely occur to the case where a machining line is provided by a plurality of machining centers which perform respective sorts of machining operations on each workpiece, but may occur to the case where each workpiece is machined by a single machining center, or to the case where each workpiece is machined by a machining device other than the machining center.
The present invention provides a machining method, a machining system, and a jig which have one or more of the following technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (24). Any technical feature that includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to the latter feature. However, the following technical features and the appropriate combinations thereof are just examples to which the present invention is by no means limited. In addition, in the case where one technical feature recites a plurality of items, it is not essentially required that all of those items be simultaneously employed. That is, it is possible to select and employ only a portion (one, two, . . . , but not all) of those items.
(1) According to a first feature of the present invention, there is provided a method of machining a plurality of workpieces in an unmanned manner, comprising the steps of holding, with a jig, a first one of the workpieces, attaching the jig holding the first workpiece, to a workpiece holding device of at least one machining device, so that the first workpiece is machined by the machining device, detaching, after the machining of the first workpiece, the jig holding the first workpiece, from the workpiece holding device, removing the first workpiece from the jig, and holding, with the jig, a second one of the workpieces, and repeating the attaching step, the detaching step, and removing step.
In the present machining method, the jig holds the workpiece, and the Jig holding the workpiece is attached to, and detached from, the workpiece holding device of the machining device. The workpiece held by the jig can be more easily and more reliably attachd and detached than the case where a workpiece is directly attached and detached. In addition, the jig has a simpler structure than that of the previously-described block which holds a plurality of workpieces, and can be used repeatedly. Thus, the present machining method can machine a plurality of workpieces in an unmanned manner without increasing the cost of equipment.
(2) According to a second feature of the present invention that includes the first feature (1), the attaching step comprises attaching the jig holding the first workpiece, to a workpiece holding device of each of a plurality of machining devices which are arranged to provide a machining line, while automatically moving the jig from an upstream one of the machining devices to a downstream one of the machining devices, so that the first workpiece is machined by the each of the machining devices.
After the workpiece is held by the jig, the jig holding the workpiece is attached to each of the plurality of machining devices, and is machined by the each machining device. In this case, the above-indicated advantage of the present invention is amplified. However, this feature is not essential. For example, a jig replacing device which replaces the current jig holding the current workpiece, with a new jig, may be provided at a place between two machining devices adjacent to each other along the machining line. In the latter case, one or more different portions of the workpiece can be machined.
(3) According to a third feature of the present invention that includes the first or second feature (1) or (2), the machining device, or each of the machining devices, comprises a machining center.
Since the machining center can perform a plurality of sorts of machining operations on a single workpiece, it is often used to machine a workpiece having a complex shape. However, it may be impossible, or not reliable if possible, to directly attach or detach the workpiece having the complex shape to and from the machining center. According to the present invention, the jig holding the workpiece is attached to, and detached from, the machining center, the workpiece can be machined in the unmanned manner with high reliability.
(4) According to a third feature of the present invention that includes the second or third feature (2) or (3), the attaching step comprises operating a movable robot which is movable along the machining line, to hold the jig holding the first workpiece, carry in the jig to the each of the machining devices, and attach the jig to the workpiece holding device of the each machining device, and the detaching step comprises operating the robot to hold the jig holding the first workpiece, detach the jig from the workpiece holding device of the each machining device, and carry out the jig.
Since the robot performs both carrying the jig holding the workpiece and attaching and detaching the jig to and from each machining device, the cost of equipment can be reduced.
(5) According to a fifth feature of the present invention that includes the fourth feature (4), the removing step further comprises operating the robot to hold the jig from which the first workpiece has been removed, and return the jig from the downstream machining device to the upstream machining device.
Since the robot additionally returns the jig from which the machined workpiece has been removed, the cost of equipment can be further reduced.
(6) According to a sixth feature of the present invention that includes the fourth or fifth feature (4) or (5), at least one of the holding step and the removing step comprises operating the robot to perform a corresponding one of attaching the first workpiece to the jig and removing the workpiece from the jig.
Since the robot performs at least one of attaching the first workpiece to the jig and removing the workpiece from the jig, the cost of equipment can be further reduced.
(7) According to a seventh feature of the present invention, there is provided a machining system, comprising at least one machining device which includes a workpiece holding device which holds a workpiece, a tool holding device which holds a tool, and a moving device which causes a relative movement between the workpiece held by the workpiece holding device and the tool held by the tool holding device, so that the workpiece is machined by the tool; a jig which includes a main body and a fixing device which fixes the workpiece to the main body; an attaching device which attaches the workpiece to the jig so that the fixing device fixes the workpiece to the main body and thus the jig holds the workpiece; a first conveying device which conveys the jig holding the workpiece, to the machining device, so that the jig is held by the workpiece holding device and the workpiece held by the jig is machined by the tool, and which receives, after the machining of the workpiece, the jig from the workpiece holding device and carries out the jig from the machining device; a removing device which removes the workpiece from the jig carried out by the first conveying device; and a second conveying device which returns the jig from which the workpiece has been removed, to the attaching device.
The present machining system can carry out the machining method according to the first feature (1).
(9) According to an eighth feature of the present invention that includes the seventh feature (7), the machining system comprises a plurality of the machining devices which are arranged in a direction from the attaching device to the removing device.
This feature is preferable to a manner in which each of the plurality of machining devices is provided with exclusive first and second conveying devices.
(9) According to a ninth feature of the present invention that includes the seventh or eighth feature (7) or (9), the first conveying device comprises a guide; and a movable robot including a movable carriage which is movable along the guide, and an operative portion which is supported by the carriage, receives the jig holding the workpiece, from the attaching device, attaches and detaches the jig to and from the workpiece holding device of the machining device, and transfers the jig to the removing device.
(10) According to a tenth feature of the present invention that includes the ninth feature (9), the second conveying device comprises the movable robot.
(11) According to an eleventh feature of the present invention that includes the ninth or tenth feature (9) or (10), the operative portion of the movable robot comprises a jig holder which holds the main body of the jig, and a workpiece holder which holds the workpiece, and selectively operates one of the jig holder and the workpiece holder.
Since the single movable robot has both the jig holder and the workpiece holder, the robot can perform at least one of attaching the workpiece to the jig and removing the workpiece from the jig, and can carry, attach, and detach the jig which holds the workpiece or from which the workpiece has been removed.
(12) According to a twelfth feature of the present invention that includes any one of the seventh to eleventh feature (7) to (11), the machining device comprises a machining center including a tool storing and selecting device which stores a plurality of tools and selects one of the tools; and a tool replacing device which automatically replaces the tool held by the tool holding device, with the tool selected by the tool storing and selecting device.
(13) According to a thirteenth feature of the present invention that includes any one of the seventh to twelfth feature (7) to (12), the fixing device of the jig continues to fix the workpiece without receiving an external action such as transmission of a force or supplying of an energy.
The present jig can be used such that after the jig holds the workpiece owing to the transmission thereto of a force, or the supplying thereto of energy, from an external device, the jig is separated from the external device so that the jig is conveyed and attached, to and detached from, the machining device.
(14) According to a fourteenth feature of the present invention that includes any one of the seventh to thirteenth feature (7) to (13), the fixing device comprises a clamp member which is engageable with the workpiece; and a clamp-member moving device which moves the clamp member to an operative position thereof where the clamp member engages the workpiece and thereby fixes the workpiece to the main body of the jig, and to an inoperative position thereof away from the operative position.
(15) According to a fifteenth feature of the present invention that includes the fourteenth feature (14), the attaching device comprises a jig holding device which holds the main body of the jig; a transferring device which transfers the workpiece to the jig held by the jig holding device; and an operating device which operates the clamp-member moving device of the jig to move the clamp member to the operative position thereof so that the clamp member fixes the workpiece to the main body of the jig.
The movable robot recited in the ninth feature (9) may be used as the transferring device.
(16) According to a sixteenth feature of the present invention that includes the fourteenth or fifteenth feature (14) or (16), the removing device comprises a jig holding device which holds the main body of the jig; an operating device which operates the clamp-member moving device of the jig to move the clamp member to the inoperative position thereof so that the clamp member releases the workpiece from the main body of the jig; and a receiving device which receives the workpiece from the jig held by the jig holding device.
The movable robot recited in the ninth feature (9) may be used as the receiving device.
(17) According to a seventeenth feature of the present invention that includes any one of the fourteenth to sixteenth features (14) to (16), the clamp-member moving device of the jig comprises a pressurized-liquid-operated actuator which is supplied with a pressurized liquid and moves the clamp member by utilizing a pressure of the liquid.
The pressurized-liquid-operated actuator may be of a double-action type in which an operative member thereof is moved in opposite directions by the pressure of the liquid, or of a single-action type in which an operative member thereof is moved in only one direction by the pressure of the liquid and is moved in the opposite direction by, e.g., an elastic force of a spring member.
(18) According to an eighteenth feature of the present invention that includes the seventeenth feature (17), the jig further comprises a liquid passage which is communicated with the pressurized-liquid-operated actuator; and a leakage preventing device which prevents, in a state in which the jig is not held by either of the attaching device and the removing device, the liquid from leaking from the liquid passage.
When the pressurized-liquid-operated actuator of the jig is operated by the operating device of the attaching device or the operating device of the removing device, the actuator needs to be connected to, and then disconnected from, a pressurized-liquid supplying device of the operating device. If the actuator remains disconnected from the supplying device, the pressurized liquid leaks from the liquid passage of the jig, naturally when the passage is further supplied with the pressurized liquid, or because of gravitational force exerted thereto when the passage is not supplied any more with the same. The present feature can avoid this problem.
(19) According to a nineteenth feature of the present invention that includes the eighteenth feature (18),the machining system further comprises a suction device which sucks a portion of the liquid that is present in a space outside the leakage preventing device; and an air supplying device which supplies air to the space.
The leakage preventing device can prevent the leakage of a portion of the liquid from a space inside the device, but cannot prevent the leakage of a portion of the liquid from a space outside the device. According to this feature, the suction device and the air supplying device cooperate with each other to suck air and replace the liquid outside the leakage preventing device, with the sucked air, thereby preventing the leakage of the liquid from the jig.
(20) According to a twentieth feature of the present invention that includes any one of the fourteenth to sixteenth feature (14) to (16), the clamp-member moving device comprises a spring member which applies an elastic force to the clamp member and thereby biases the clamp member toward the operative position thereof; and a clamp-release member which moves, owing to an external force exerted thereto, the clamp member to the inoperative position thereof against the elastic force of the spring member.
The present clamp-member moving device enjoys a simple construction.
(21) According to a twenty-first feature of the present invention that includes any one of the fourteenth to sixteenth feature (14) to (16), the clamp-member moving device comprises an externally threaded member and an internally threaded member which are threadedly engaged with each other, and one of the externally threaded member and the internally threaded member is connected to the clamp member and the other of the externally threaded member and the internally threaded member is rotatable about an axis line and is not movable in a direction parallel to the axis line.
The operating device of the attaching device or the operating device of the removing device may be provided by a rotating drive device.
(22) According to a twenty-second feature of the present invention that includes the twenty-first feature (21), the clamp-member moving device further comprises a rotation preventing device which is selectively switchable to a first state thereof in which the rotation preventing device prevents a rotation of the other of the externally threaded member and the internally threaded member and to a second state thereof in which the rotation preventing device permits the rotation.
The present clamp-member moving device can stably maintain the clamp member at the operative position thereof.
(23) According to a twenty-third feature of the present invention, there is provided a jig, comprising a main body; and a fixing device which continues to fix a workpiece to the main body without receiving an external action such as transmission of a force or supplying of an energy, the fixing device comprising a clamp member which is engageable with the workpiece; and a clamp-member moving device which moves the clamp member to an operative position thereof where the clamp member engages the workpiece and thereby fixes the workpiece to the main body, and to an inoperative position thereof away from the operative position, the clamp-member moving device comprising a spring member which applies an elastic force to the clamp member and thereby biases the clamp member toward the operative position thereof.
The present jig may employ any one of the seventeenth to twentieth features (17) to (20).
(24) According to a twenty-fourth feature of the present invention that includes the twenty-third feature (23), the clamp-member moving device further comprises a pressurized-liquid-operated actuator which is supplied with a pressurized liquid and moves, by utilizing a pressure of the liquid, the clamp member to the inoperative position thereof.